1. Field of the Invention
This invention relates to a tube connecting unit for joining a tube to, for example, a device that feeds air to a pneumatically operated machine. The fluid fed through the tube is not limited to air but may be other types of gases or liquids.
2. Description of the Prior Art
A conventional device of tube connector is, for example, disclosed in the Japanese Utility Model Laid-open Publication No. 120485 of 1981 (Jitsu-kai-sho 56-120485).
In the above conventional tube connector, a tube has a fastening part formed by expanding one end thereof. An O-ring is fitted over the tube. The tube is fitted in a small bore of a cap nut which is screwed onto the connector. Thus, the tube is fastened to the connector while the fastening part and O-ring are hermetically held between the inner wall of the cap nut and the inner wall of the connector.
In the conventional fastening method just described, a tube is fitted by screwing together a connector and a cap nut. The cap nut must then be tightened with a tool by exerting a predetermined torque. This tightening operation has been inefficient. The inefficiency increases when the connector is fastened to a machine or the like installed in a limited space.